The invention relates to an imaging unit of a camera for recording the surroundings using an image sensor, to which one lens is allocated to display the surroundings on the image sensor, whereby the image sensor is held by a carrier, and with a circuit board arranged on said carrier and which has at least the signal and the supply lines of the image sensor.
Such imaging units are used for various applications, e.g. for stereoscopic cameras, in order to control the movement of a mobile device based on the optically recording and processing of the surroundings. In order to realize possible functions of the device, its positioning, as well as avoiding any collisions when in motion, it is necessary to constantly detect objects of the surroundings and their distance from the device, and to supply it for real-time processing.
The design of such an imaging unit of a camera regularly comprises an electronic image sensor, to which a lens is allocated, which is adjusted to the respective application and also the sensor. The image sensor is mounted on a circuit board, on which signal lines, supply lines, and if applicable at least preliminary signal processing units are arranged.
The circuit board including the described structures is mounted on a carrier. The lens is arranged above the image sensor at a distance that is necessary according to the optical system of the lens. It is mounted onto the carrier and the circuit board in such a way, so that the image sensor is entirely encased, and light only impinges on the image sensors through the lenses. If necessary, the lens has a separate housing for this purpose.
The carrier and also its connections to the circuit board and the lens or its housing must meet various mechanical, thermal, chemical, and electrical requirements for the different applications, whereby the mechanical stability is to be ensured especially for the use in mobile devices. For this reason, the carriers are usually made of metal.
Furthermore, the thermal expansion behavior of the carrier and that of the circuit board mounted permanently onto the carrier affects the images taken by the camera. The different expansion coefficients of the two materials connected to each other lead to a shifting of the image sensors relative to their lenses because of the heat created by the electronic components when operating. Therefore, a loss of image quality is detected, e.g. during extended operating, in particular for a stereoscopic camera. In this way, the interferences are caused by diffused light, which impinges on an image sensor through defective connections between the carrier and the lens. The connections between the carrier and the lens are mostly adhesive connections, which can tear away from the carrier and the lens due to thermal expansions.